AMD Athlon II X4 631 socket: Socket FM1

What the Athlon II X4 631 is

AMD Athlon II X4 631 is a quad core Llano processor that AMD released in August 2011 for socketed desktops. It uses the Stars K10 core design on a 32 nm process, running at 2.6 GHz with no turbo. The cache is 4 MB of L2 with 1 MB per core and no L3. Power is 100 W. There are no integrated graphics on this Athlon variant, so a separate card is required for any display output. A 65 W stepping followed in 2012, but this page covers the August 2011 100 W part.

The four cores carry 1 MB of L2 each with no L3, and threads equal cores at 4. The chip is a Llano die with the graphics block disabled, which is why it needs FM1 rather than AM3. Each core keeps its own floating point unit for predictable single thread behavior.

At 100 W the Athlon II X4 631 fits mid towers with tower air cooling. The 2.6 GHz fixed clock suits office multitasking without tuning. Boards pair it with DDR3 DIMMs and SATA drives. The How to find your CPU socket type guide shows how to confirm the socket before ordering parts.

Socket and motherboard compatibility

The Athlon II X4 631 fits Socket FM1 on A55 and A75 boards. The 905-contact socket accepts Llano APUs and Athlon derivatives, but BIOS support still decides each model. DDR3 modules match stock operation without tuning.

Power delivery suits the 100 W rating. A board that lists Llano Athlon support is the safe choice. The CPU cooler compatibility by socket guide explains the 48 by 96 mm pattern shared with AM2, AM3 and FM2.

Memory, PCIe and cooling

Memory support is DDR3 up to 1866 MT/s, two channels. Boards commonly offer four DIMM slots on ATX and two on micro ATX. Two matched modules give the rated bandwidth.

PCI Express is PCIe 2.0 from the CPU for one graphics slot with 16 lanes, since every Athlon FM1 build needs a separate card. A mainstream card of the era pairs without waste. SATA and USB come from the Hudson controller hub.

Cooling follows the 100 W rating. A tower air cooler with a 120 mm fan is the practical pick.

Upgrade paths

Within Socket FM1 the Athlon II X4 631 can move to faster Athlon quads or to Llano APUs with graphics on the same board. Memory, storage and the graphics card carry over. A faster Athlon comparison is AMD Athlon II X4 651 on the same socket.

A platform move means a new socket. AMD moved mainstream desktops to Socket FM2 with Piledriver cores. That move needs a new board while DDR3 memory often carries over.